Bilingual Heterogeneity in Speech: "Typical" Trends and "Atypical" Cases in Disfluency

Bilingual children's speech often contains high percentages of disfluencies in both their languages; however, the distribution of disfluency types and the difference across bilinguals' two languages have received insufficient and inconsistent empirical support. The present research aims to profile "typical" bilingual disfluency phenomena while comparing across the two languages and examining the impact of language exposure as well as proficiency.

The current research analyzed disfluency rates and types among 32 bilingual children aged 4-9 years speaking a heritage language (HL; English or Russian) and a societal language (SL; Hebrew). Children's language proficiency was examined using a receptive vocabulary task and a sentence repetition task in both HL and SL. Analyses of three speech samples (spontaneous speech, narrative telling, and narrative retelling) were conducted examining rates and types of stuttering-like disfluencies (SLDs) and other disfluencies (ODs).

The percentage of SLDs was higher in SL than in HL, which was related to the amount of exposure, whereas the percentage of ODs was associated with the proficiency vocabulary score and age of onset of bilingualism. Analysis of individual profiles revealed that nine children had high SLDs in at least one language. This could lead to stuttering overdiagnosis. Children whose SLD rates were high in both languages showed low performance (1 SD below the group level) on proficiency tasks, whereas children with a high percentage of SLDs only in HL had intact proficiency.

The results reveal high individual variation in disfluencies and support the importance of SLD-OD distinction in research on bilingual disfluency. Clinical implications of the research suggest that assessment of bilingual speech should be conducted applying unique criteria, different from the existing monolingual norms.